A liquid ejection apparatus, such as a print apparatus, is loaded with a liquid container containing a liquid in the interior, as a supply source of the liquid. The liquid container is loaded into the liquid ejection apparatus so as to be detachable therefrom, and when there is no longer any liquid in the interior, the liquid container can be replaced with a new liquid container.
Techniques for determining whether or not there is liquid inside a container by using a detection element have been proposed, with the purpose of informing a user of the timing for replacing the liquid container. In, for example, a technique disclosed in Japanese Laid-open Patent Application No. 2003-260804, a prism serving as a detection element is installed at a bottom surface of a detection chamber within a liquid container; light is incident on the prism from a light-emitting element, and the reflected light is detected with a light-receiving element. In a state where the surface of the prism is not exposed from the liquid (a state where liquid still remains within the liquid container), the light does not return, and thus light is not detected at the light-receiving element, but when the prism is exposed from the liquid, then the light reflected by the prism is detected at the light-reflecting element. For this reason, depending on whether or not light is detected at the light-receiving element, it is possible to determine whether or not there is liquid inside the liquid container.